Evidence supporting the involvement of MHO in the formation of superficial scald in ‘Dangshansuli’ pears

Abstract

The development of superficial scald in ‘Dangshansuli’ pears (Pyrus bretschneideri Rehd) was investigated in relation to 6-methyl-5-hepten-2​​-one (MHO). Over the course of a 180-day cold storage at 2±0.5°C and a 9-day post storage at 20°C, the effect of endogenous MHO was investigated in chemically untreated pears, and pears treated with diphenylamine (DPA) and 1-methylcyclopropene (1-MCP) after harvest. In the untreated pears, MHO began to accumulate in peel tissue after 60 d of cold storage and continued to do so until the end of cold storage, by which time superficial scald had developed. In DPA- and 1-MCP-treated pears, on the other hand, there was very little MHO accumulation during cold storage and, at the end of this period, no scald had developed. Results from the cold storage period, therefore, indicate a positive relation between scald incidence and endogenous MHO concentration. Results from 9-day post-storage reveal also a strong positive correlation between scald and endogenous MHO concentration, with a correlation coefficient of 0.97936 (P<0.05).The effect of exogenous MHO was investigated before and after cold storage in DPA- and 1-MCP-treated pears, as well as untreated pears. The application of 0.5, 1.0, and 2.0mLL−1 MHO both before and after cold storage caused scald develop in a concentration-dependent manner: The higher the MHO concentration, the higher the scald incidence. The application of DPA and 1-MCP prior to application of MHO did not affect scald development before cold storage. However, after cold storage, DPA-treated pears were found to have a lower scald incidence and MHO concentration than untreated pears. Moreover, the results indicate that MHO directly induces superficial scald in ‘Dangshansuli’ pears.